Method for joining waxed paperboard surfaces



I. G. NICHOL April 11, 1967 METHOD FOR JOINING WAXEDPAPERBOARD SURFACES Filed Nov. 6, 1965 FIGFZ I IIIIIIIIH 1 '1 INVENTOR. IVEN G. NICHOL 7% I21 4 1 J I BY MORGAN,FINNEGAN, DURHAM 8| PINE ATTORNEYS FIG-4 United States Patent 3,313,218 METHOD FOR JDINING WAXED PAPERBOARD SURFACES Iven G. Nichoi, Stamford, Conn, assignor to Morningstar-Paisley, Inc., New York, N.Y., a corporation of Delaware Filed Nov. 6, 1963, Ser. No. 321,354 3 Claims. (Cl. 9336) This invention relates to a new and improved process for joining paper or paperboard surfaces. More particularly, the present invention relates to a new and improved process for joining wax covered paper or paperboard surfaces in the formation of containers for foodstuffs and the like. Although, generally speaking, the invention relates to the joining of overlapping flaps and side seams of paperboard containers the invention is not limited to this particular embodiment.

In the packaging industry it is common to coat the surface of the paper or paperboard surface with wax by what is known as the cold water wax process or the hot wax process where the wax is applied by a roll over the entire area of the container. As used herein the term cold water wax to refer to that process wherein the wax after application to the paperboard is immediately chilled by low temperature water, whereas the hot wax process refers to the process wherein molten wax is applied to the paper or paperboard surface and allowed to cool at room temperature. The resent invention has been found to be useful where the coated container has been made in accordance with either of the processes described generally above.

A serious and difficult problem has arisen in the packaging industry when efforts have been made to join the flaps of wax covered paperboard cartons. The problem is similar whether the flaps extend longitudinally of the carton or transversely thereof. More specifically, no atisfactory method or process has been found prior to the invention for applying hot melt adhesives to paperboard wax covered surfaces. The main reason for the unsatisfactory practices of the past was that the hot melt glue would not adhere to the wax surfaces when app-lied in conventional manner at commercially desirable speeds. Since the glue would not adhere to the wax covered surfaces, the surfaces would not be properly joined. It can be appreciated that in commercial production an extremely high speed operation is necessary. Accordingly, in prior art devices means have been provided for removing wax from the surface of the flap in the area where the glue is to be applied and in the area where the two flaps are joined together. Although this procedure has resulted in a fairly satisfactory gluing of the paperboard surfaces often unsightly marks on the carton surfaces occur and sometimes the wax and board stock are scorched which may even cause a toxicity problem or odor problem for foods. It is also obviously a time-consuming and expensive task requiring additional equipment. Thus, such prior art devices have required additional equipment and have not been entirely satisfactory thereby increasing the cost, expense and time of the gluing operation as well as the appearance and possible health problem. Another prior art method has been to wax the carton only in selected portions in a manner whereby the wax is not applied to the surfaces of the carton where the glue is to be applied. This prior art process made the wax applying process unduly complicated giving slower production rates during the waxing and sealing and requiring the use of special equipment and the exercise of special care to keep all wax from the areas to be glued.

In accordance with the present invention a new and improved process is provided for applying hot melt glue to wax covered paperboard surfaces wherein no special waxing or dewaxing equipment is needed and the cartons can be glued at a speed in conformity with commercial speed requirements. The present invention is particularly adapted for applying what is known in the art as hot melt adhesive.

In accordance with this invention the hot melt glue is applied at an elevated temperature whereby wax on the first flap coming into contact with the hot melt adhesive melts the wax and the glue is mixed with the molten wax. When the second fiap comes into contact with the hot melt adhesive applied to the first flap, the wax on the second flap is also melted and the two flaps can be joined together allowing the adhesive to come into contact with both paperboard surfaces without the wax between the adhesive and the board stock.

The present invention is applicable to and of great value in applying glue of various formulations to wax covered surfaces wherein the wax may have different melting points. Since the temperature to which the glue is heated prior to application increases as the melting point of the wax increases for a given wax formulation and for a given speed of the carton, the temperature of the glue is dependent upon, at least to some extent, the melting point of the wax.

In general, the melting temperature of the wax will have a range between about 165 F. As will be explained more completely hereinafter, typical wax formulations may have melting temperatures of 138140 F., 140l42 F. and in some instances, the melting temperature of the wax will be higher. The glue in accordance with this invention must be heated to an elevated temperature substantially above the melting temperature of the wax. The glue in accordance with this invention must be heated, however, to a temperature sufiiciently high to melt the wax on the paperboard surface to which it is directly applied as well as to melt the wax on the paperboard surface which is to be joined to the paperboard surface to which the glue is directly applied. Generally, then the glue is heated to a temperature of between about 325 45O F. For most wax formulations the glue is heated to a temperature of between 350400 F. In one specific preferred embodiment where the wax has a melting temperature of between 138 F.140 F.

the glue was heated to a preferable temperature of 350 F. to 375 F.

In accordance with the invention a wax covered carton blank is moved towards a glue applying station where the glue at a temperature suflicient to melt the wax is applied to one flap of the carton. The glue is applied by a roller which, in accordance with this invention is rotating in a direction opposite from the direction of movement of the carton. In this manner the glue is applied more evenly and uniformly than where the glue roll is moving in the same direction as the carton blank. In most instances, if the roll is moving in the same direction and at the same speed as the carton blank the glue will not even transfer to the carton blank. In some instances,

however, satisfactory results have been obtained where the glue roller is rotated in the same direction as the carton blank where there is a speed differential of at least 25% between the carton blank and the roller.

Immediately after the hot melted glue has been applied to a first flap, a second flap is folded over the first flap and the two flaps are then pressed together for a length of time sufficient to insure that the two flaps are joined together.

In view of the foregoing it is an object of the present invention to provide a new and improved method of gluing wax covered flaps or side seams.

Another object of this invention is to provide a new and improved method of applying hot liquid glue to paperboard wax covered flaps at an elevated temperature so that the hot glue will melt the wax on both flaps and the two flaps will be joined together.

A still further object of this invention is to provide a method of applying hot glue to a wax covered surface with a roller that is moving in a direction opposite from the direction of movement of the wax covered surface.

Another object of this invention is to provide a method of applying glue to a wax covered surface where the glue is applied at an elevated temperature by a roller moving in a direction opposite from the direction of movement of the wax covered surface, the temperature being sufficiently high to melt the wax on a second wax covered surface when it comes into contact with the first wax covered surface.

Other objects and advantages of the invention will be set forth in part hereinafter and in part will be obvious herefrom or may be learned from practicing the invention. The same being realized and attained by means of the process and combination of steps pointed out in the appended claims.

The invention consists in the novel steps, procedures, processes, combinations and improvements herein shown and described.

The accompanying drawings which are incorporated in and constitute a part of this specification illustrate an embodiment of the invention, and together with the description serve to explain the principles of the invention.

Of the drawing:

FIGURE 1 is a perspective view of a partially formed container.

FIGURE 2 is a schematic view of a glue applying device.

FIGURE 3 is a plan view showing the hot glue being applied to the carton blank in a schematic manner.

FIGURE 4 is a side elevation view of the step shown in FIGURE 3.

FIGURE 5 is a plan view showing the carton blank after the glue has been applied to one of the flaps and the flaps are being closed.

FIGURE 6 is a side view of the step shown in FIG- URE 5.

FIGURE 7 is a plan view showing the first step in the closing of the end flaps.

FIGURE 8 is a side view of the step shown in FIG- URE 7.

Reference now will be made to the accompanying drawings wherein a preferred embodiment of the present invention is described.

In FIGURE 1 there is shown an unsealed paperboard carton blank 2 which is adapted to be sealed into a carton so that it can be used as a package or container for protecting various items such as foodstuffs. The paperboard has been coated by either the cold water wax process or the hot wax process and accordingly has a coating of wax therein. The wax, which may be of any one of several formulations normally has a melting temperature in the range of 130l65 F. but in one preferred embodiment has a melting temperature of 138l40 F. while in another preferred embodiment has a melting temperature of 140-142 F. As will be explained subsesequently in some instances, the melting temperature may be higher. The present invention in its broader aspects is not necessarily limited to any particular wax formulation or any particular wax melting temperature range. It will be noted that the carton includes a plurality of flaps, 4, 4A which can be folded with respect to one another to thereby form a package with flap 4 overlying flap 4A. This invention is directed to the problem of joining by means of hot liquid glue two of the surfaces which are covered with wax.

Although no particular form of apparatus is necessary to the practice of the present invention, one type of glue applying apparatus which can be effectively used in carrying out the present invention is partially shown in FIGURE 2. In that figure there is shown what is known as a glue pot 6 in which glue is placed while in solid form and subjected to heat to thereby melt the adhesive so that it changes from a solid to a liquid form. The hot melt adhesive or glue is heated to a temperature in the range of 325-450 F. and preferably in the range of 350-400 F. Rotatably mounted within the glue pot so that a portion thereof is continually in contact with the hot glue is a glue applying wheel 8. The glue applying wheel also extends above the upper surface of the glue pot so that the surface thereof can apply the liquid glue to the surface of a flap 4 located adjacent thereto. It is customary in the packaging industry for the carton blanks to be fed past the glue pot while on a conveyor or the like and for the glue wheel to be rotated by conventional means such as a motor or drive (not shown) so that hot melt adhesive is continuously applied to the carton blank with the roll normally moving in the direction of travel of the carton at a synchronized speed with the carton. For reasons to be described more completely subsequently, an important novel feature of this invention. is the direction of rotation of the glue applying wheel.

After certain preliminary steps not relevant to the present invention, the carton blank takes the form shown in FIGURE 1 where two flaps, 4 and 4A, have been moved to a position whereby these flaps can be joined together by means of a hot liquid adhesive in the manner to be subsequently described.

As shown in the drawings, the flaps about to be joined are the end flaps of the carton. The invention is not limited to the joining of end flaps but is also applicable to joining the longitudinally extending flaps more commonly called side seams.

Several different wax formulations have been utilized successfully in the practice of this invention, examples of which are given below. It is to be understood, however, that the invention is not limited to joining flaps having any particular wax formula thereon.

One example is a hot or cold Water chilled wax coating known in the trade as Conoco food grade wax having a melting point of 138 F. to 140 F. Another example of a typical wax formulation is a wax consisting of paraffin and 5% of a low molecular weight polyethylene with a melting point of about 138 F. to 140 F. Where a Wax coating having a 20% low molecular weight polyethylene was used, then the melting temperature of the wax may be above 142 F. and about F.

In the practice of the invention the hot melt adhesive is heated to a molten state and maintained in the glue pot at a temperature of between 325 F. and 450 F. and preferably between 350 to 400 F. and with some waxes between 350375 F. Typical examples by weight of the glue formulation desirable in the present invention are:

Parts Ethylene-vinyl acetate copolymer with a low melt index 20 Ethylene-vinyl acetate copolymer with a high melt index 15 Microcrystalline wax 30 Wood resin 35 Parts Ethylene-vinyl acetate copolymer low melt index 15 Ethylene-vinyl acetate copolymer high melt index 20 Microcrystalline wax 30 Glycerol ester of hydrogenated resin 35 Ethylene-vinyl acetate high melt index 20 Microcrystalline wax 35 Alpha-terpene resin 45 It will be appreciated that the foregoing examples are exemplary and not restrictive of the glues which can be used in the practice of this invention.

In accordance with this invention, hot liquid glue is applied to the carton while at a temperature of between 350400 F. It is believed that one of the reasons for the success of the present invenion is that when the hot glue is applied at this temperature, the wax on the paperboard melts and the glue is mixed with the wax but does not lose its adhesive quality. Another possible explanation for the success of the present invention results from the fact that the wax when heated by the hot glue is absorbed to some extent at least by the paperboard and the glue does not lose any of its adhesive qualities.

In accordance with this invention the glue is applied in a novel manner whereby the direction of the glue applied is opposite from the direction of movement of the carton blank to thereby insure complete and even penetration of the glue through the wax and enabling the hot melt adhesive to spread evenly on the carton flaps.

This result is accomplished in the present invention by rotating the glue applying wheel 8 in a direction which is opposite to the path of travel of the carton. As shown in FIGURES 2-4, the carton blanks are proceeding the direction shown by the arrow A whereas the wheel 8 is rotating in a direction shown by the arrow B which is opposite to the direction of movement of the carton blanks.

In this preferred form of the invention a vortex of glue 10 is formed between the wheel and the carton in the direction in which the carton is passing. With this embodiment of the invention, the hot glue is applied evenly to the carton and the wax is effectively removed from the surfaces of the flaps to be joined together and blended into the hot melt adhesive.

As shOWn in FIGURES 2-4 the glue applying wheel comes in contact with the undersurface of one of the flaps such as flap 4. The temperature of the glue is sufficiently high so that when the second flap 4b comes into contact with the first flap (FIGURES 78), the wax on that surface will be melted as in the case of the first flap. As shown in FIGURES 5-6 after flap 4 has been coated with glue on the undersurface as shown at 12 in the next step of the carton forming operation the two flaps are placed in superimposed position, i.e., one on top of the other as shown in FIGURES l8. As noted above, the temperature of the glue which has been applied to the undersurface of flap 4 is sufiicient to melt the wax on the surface of the flap 4a when it comes into contact with the surface of the first fiap. In order to insure the proper functioning of this invention the time elapsing between the steps illustrated in FIGURE 2 and that of FIGURE 5 is only a few seconds at best. It is desirable to combine the flaps at once. As shown in FIGURES 7-8, the flaps are moved into a closed position while in the guideway 14 to thereby close one flap over the other.

The closed flaps 4-4a when in the guideway 14 are subjected to a light pressure which is snfiicient to maintain the over-lapping flaps 4-4a in the closed position for a suificient length of time which will enable the glue to set.

The advantages of the present invention can be seen from the several illustrative examples given below.

6 Example 1 A carton blank having a coating of paraffin wax with a melting point of 138 F.l40 F. the end flaps were sealed by applying a hot melt glue having a temperature of 350 F. to 375 F. while carton fiaps were fed to a glue applying roll having a direction of rotation opposite to the direction of feed of the cartons. The cartons were fed at a rate of 40-75 per minute and the conveyor was moving at a rate of 150-200 feet a minute. The glue roll was rotating at a rate of 200-300 revolutions per minute. It was found that the flaps were glued in a completely satisfactory manner.

Example 2 In another example butter carton blanks having a wax covering with a melting temperature of 138 F. to F. Were fed past the glue pot up to a rate of 40,000 per hour at a linear speed of 350-800 feet per minute. The hot glue at a temperature of 375 F.400 F. was applied by a rotating roller moving in a direction opposite to the carton blank having a surface speed of between 500 and 1200 feet per minute. In this example, it was noted that the temperature of the hot glue had to be increased with the speed of the carton blank. It was found that the longitudinal flap (side seam) were joined in a completely satisfacto manner.

Iy Example 3 In another example ice cream cartons were fed at a rate of 2025,000 per hour by a conveyor belt having a speed of between 400600 feet per minute. The glue applying roll was rotated at a surface speed of about 1000 feet per minute in a direction opposite to the direction of the carton blank and the glue was applied at a temperature of 375 400 F.

Here it can be noted that the temperature had to be maintained near 400 F. even though the conveyor speed was slower. The wax coating was heavier making it necessary to carry a higher temperature to melt the heavier wax coating. In this run of ice cream cartons both 138 F.l40 F. wax coating as well as a coating with 5% additional low molecular weight polyethylene were run satisfactorily. It was found that the longitudinal flap (side seam) was bonded in a completely satisfactory manner.

It should be noted that a wax type coating where 20% low molecular weight polyethylene was added a hot melt temperature of 425 F. was required to melt this coating and run satisfactory because the melting temperature of this wax coating was higher.

The invention in its broader aspects is not limited to the specific embodiments shown and described, but departures may be made therefrom, within the scope of the accompanying claims, without departing from the principles of the invention and without sacrificing its chief advantages.

What is claimed is:

1. In the formation of paperboard containers or the like from wax-covered blanks having flap portions and wherein the wax melts at a predetermined temperature, a process of joining two of said flap portions comprising: moving said blank toward a glue applying station including a roller rotatably mounted in a supply of hot melt glue, heating said supply of glue at said station to a temperature substantially above the melting temperature of the wax on said blank, forming a pocket of said heated glue between said blank and the peripheral surface of said roller by rotating said roller in a direction opposite to the direction of movement of said blank, applying said glue to one side of one of said flaps from said pocket while at said heated temperature, substantially immediately thereafter moving said flaps toward one another until they are in superposed position and the applied glue contacts one side of the other of said flaps, applying pressure to said flaps while in said superposed position to thereby melt the wax on the facing sides of both of said flaps, and maintaining said pressure on the flaps until the glue has set.

Y 8 2. The process as claimed in claim 1, wherein said wax References Cited by the Examiner coating melts at a temperature of l38140 F. and said UNITED STATES PATENTS glue is heated and applied to said one of said flaps at a temperature of 350400 F. gigi i 3. The process as claimed in claim 1, wherein said Wax 5 28833O3 4/1959 Jennin'gs coating melts at a temperature of 130-165 F. and said 3140215 7/1964 Russell 93 36 glue is heated and applied to said one of said flaps at a temperature of 325 45 0 F. BERNARD STICKNEY, Primary Examiner. 

1. IN THE FORMATION OF PAPERBOARD CONTAINERS OR THE LIKE FROM WAX-COVERED BLANKS HAVING FLAP PORTIONS AND WHEREIN THE WAX MELTS AT A PREDETERMINED TEMPERATURE, A PROCESS OF JOINING TWO OF SAID FLAP PORTIONS COMPRISING: MOVING SAID BLANK TOWARD A GLUE APPLYING STATION INCLUDING A ROLLER ROTATABLY MOUNTED IN A SUPPLY OF HOT MELT GLUE, HEATING SAID SUPPLY OF GLUE AT SAID STATION TO A TEMPERATURE SUBSTANTIALLY ABOVE THE MELTING TEMPERATURE OF THE WAX ON SAID BLANK, FORMING A POCERAL SURFACE OF GLUE BETWEEN SAID BLANK AND THE PERIPHERAL SURFACE OF SAID ROLLER BY ROTATING SAID ROLLER IN A DIRECTION OPPOSITE TO THE DIRECTION OF MOVEMENT OF SAID BLANK, APPLYING SAID GLUE TO ONE SIDE OF ONE OF SAID FLAPS FROM SAID POCKET WHILE AT SAID HEATED TEMPERATURE, SUBSTANTIALLY IMMEDIATELY THEREAFTER MOVING SAID FLAPS TOWARD ONE ANOTHER UNTIL THEY ARE IN SUPERPOSED POSITION AND THE APPLIED GLUE CONTACTS ONE SIDE OF THE OTHER OF SAID FLAPS, APPLYING PRESSURE TO SAID FLAPS WHILE IN SAID SUPERPOSED POSITION TO THEREBY MELT THE WAX ON THE FACING SIDES OF BOTH OF SAID FLAPS, AND MAINTAINING SAID PRESSURE ON THE FLAPS UNTIL THE GLUE HAS SET. 